(a) Technical Field
The present invention relates to a method for preparing hollow carbon fibers having an empty space in the cross section thereof.
(b) Background Art
With a growing concern on the depletion of petroleum resources, and environmentally safe resources worldwide, there has been a continued interest in improving fuel efficiency in vehicles. As a result, research for reducing the weight of a vehicle has been conducted, and one most efficient ways to reduce the weight of a vehicle is through the application of carbon fiber composite parts. The carbon fiber in the carbon fiber composite, however, has a higher specific gravity than resin, its parent material. Thus, if the strength of a carbon fiber is maintained, while reducing the specific gravity of the carbon fiber, weight reduction can be better achieved.
In an effort to further reduce the weight of carbon fibers, hollow carbon fibers having an empty space in the cross section thereof has been introduced. Typically, a fluid is fed into the center of a spinneret during spinning of precursor fibers to prepare hollow fibers, and the fibers are stabilized and carbonized to prepare hollow carbon fibers. [U.S. Pat. Nos. 5,338,605 and 4,358,017]
However, this method is inefficient because it requires a high amount of energy consumption to use and collect the fluid (gas, liquid). The fed fluid increases the solidification speed of an extruded acrylonitrile copolymer spinning solution, which is predominantly used for carbon fiber precursor preparation. Thus, it is difficult to produce carbon fibers with a high degree of strength, and with a diameter appropriate for use as a structural reinforcement. Accordingly, the carbon fibers produced by this method, instead are in actuality used for heat insulation, and thus their use is limited.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.